The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
One sensor that may be used within a vehicle is an in-cylinder pressure sensor. The in-cylinder pressure sensor provides feedback for operating the engine. The in-cylinder pressure sensor signal may have a significant amount of noise. Low-pass filtering with a band pass filter may distort the signal to unacceptable levels so that pressure data may not meet the accuracy requirements for the entire engine cycle.
Cylinder pressure sensing may be used to control various functions in an engine. In a homogenous charge compression ignition (HCCI) engine, a level of heat released during a compression cycle may be used to control the engine. The amount of heat released may be determined in part using the in-cylinder pressure sensor. However, because of the high signal noise associated with the in-cylinder pressure sensing, it is difficult to resolve the low level of heat released during an HCCI exhaust recompression cycle.